Assigstob



as. VERNAM TELEGRAPH SYSTEM Original Filed Dec. 1927 INVENTOR. G. S. Verna/0w ATTORNEY Nxf mxx Nov. 19, 1929.

' the distant station.

Patented Nov. 19, 1929 nane FAENT FlFltE GILBERT S. VERNAM, 0F RIVER EDGE, IJEXV JERSEY,

ASSIGNOB TO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK TELEGRAPH SYSTEM Application filed December 3, 1927, Serial This invention relates to telegraph systems and more particularly to improved arrangements for reducing interference on such systems caused by sudden surges of current thereover, particularly by such surges of current as might be caused from lightning or othersources extraneous to the telegraph system.

Surges of current caused by lightning are propagated over open wire telegraph circuits and are likely to actuate the relays of repeaters-or other apparatus along the circuit causing them to repeat false signals. These false signals are usually impulses of short duration. Various means have been tried in the past for reducing the number of such false signals or kicks due to sudden undesired surges of current, but none of such means have been successful in entirely elimi- Other objects and features of the invention will appear mor fully from the detailed de scription thereof hereinafter given. I

It is the practice in telegraph systems, when an operator is sending from one station, to provide arrangements thereat whereby an operator at a distant station may interrupt or break the operator at the first station by transmitting impulses back over the line from Obviously, these break arrangements might ordinarily be effected by surges on the circuit due to lightning or other causes. In general, the arrangements of the present invention provide a suflicient delay in the break arrangements associated with a station so that they will not be effected by these surges or impulses of short duration due to lightning or other causes. However, the breaking may be accomplished by the transmission of a slightly longer break signal than heretofore.

In the ordinary half-duplex telegraph cir- 1%. 237,521. Renewed June s, 1928.

cuit, the telegraph signals are transmitted in one direction at a time. False signals or kicks due to lightning, however, may be repeated in either or both directions over the line. The slow break arrangements of the present invention will prevent any brief false g is or kicks from being repeated back over the line circuit 111 adirection opposite to that in which the telegraph signals are being transmitted but will have no effect-on such impulses that are transmitted in the same direction as the telegraph signals.

The benefit to be derived fromthe arrangements of the invention will depend upon the line lay-out, the direction in which most of the trallic is transmitted. and other factors. For the purposes'of illustration, a typical circuit 'to which the arrangement of the invention might be applied will be briefly outlined. A circuit might be constructed from New York and Washington to Chicago and thence to St. Louis. It might be that such a circuit would be utilized for press dispatches and that most of the transmission would be from New York and lVashington to points west. The circuit from-lVashington and New York to Chicago might be in cable and not subject to lightning interference. The circuit from Chicago to St. Louis might be an open wire circuit and hence subject to interference. Lightning in- .terference 1n the open wire section between Chicago and St. Louis would normally cause "kicks that would be repeated at Chicago, causing errors at all stations and obviously breaking and interrupting the sending station either at lVashington or New York. This would be particularly undesirable if high speed printers were eing used as in many cases an entire page of copy might have to be rerun to correct the error. Accordingly, the slow break circuit arrangements ofthe invention would be applied to the circuit at the repeater station at Chicago. Under such conditions, while message si nals were being sent from the east, no short false signal impulses from th line section between Chicago and St. Louis could be repeated either to local printers at Chicago or to the lines toward the east from Chicago. However, a long break signal from St.

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Louis would be repeated through the Chicago arrangements so that the St. Louis operator could interrupt sending from the east, if necessary. The above circuit lay-out illustrates the advantage of applying slow break arrangements of the invention to prevent lightning kicks from being repeated from an open wire to a cable circuit. It is pointed out, however, that the circuit arrangements of the invention can also be applied to advantage in many cases where only open wire lines are involved, particularly in connection with high speed printer service on lines having a fairly large number of stations. In such cases, it might be applied to both sides of one or more intermediate repeaters.

The slow break arrangements of the invention consist essentially of one or more slow release relays associated with the duplex set or other type of repeater. These relays remain energized while signals are being transmitted through a repeater toward the open wire line and prevent any short false signal impulses that may come in over the open wire line from being repeated back. The slow release relays are deenergized when transmission toward the open wire line stops and they can also be released by a long break signal from the open wire line. When released, the relays have no effect on the repetition of signals by the repeater. The slow break device of the invention therefor has no effect on the usual telegraph service except to require a somewhat longer break signal in order to interrupt sending in one direction.

The invention may be more fully understood from the following description together with the accompanying drawing in the ligure of which is shown a circuit diagram embodying a preferred form of the invention.

In the drawing is shown a telegraph repeater comprising a bridge polar duplex set. An incoming open wire line 1' will be asso ciated with a polar receiving relay 2 of this set, an artificial line 3 will also be associated with said relay. The apex of the-artificial line and the open wire line will be connected to the armature of a sending relay l. This relay will control the application of currents of dilferent polarities to this armature and thence to the line 1 for sending purposes. The sending relay 4 may be controlled either by the key 5 or by apparatus in the receiving loop 6. The receiving loop 6 may be connected to other repeater apparatus so as to form an intermediaterepeater to extend the circuit to other stations. The armature of the receiving relay 2 is connected over the contact of the slow release relay 13 to the winding of a control relay 7. The slow release relay 13 will in turn be controlled by other slow release relays such as 11 and 12. This chain of relays will be controlled by the operation of relay 9 which in turn is dependent upon the operation of the sending relay 1. The invention may be more fully understood from the following description of its operation.

hen signals from another line circuit associated with this repeater or from alocal telegraph set or printer are repeated inloop circuit 6, the sending relay 4: will operate to send positive or negative impulses to the line 1 and artificial line 3 in the usual manner. The armature of the polar receiving relay 2 will normally be held by current from the distant line battery against its marking or upper contact as shown and will not respond to these outgoing signals. The relay 9, however, will respond to these signals as it is operated from the auxiliary contacts of the sending relay 4-. The relay 9 sends impulses from its back contact through the contact of key 10 and the winding of slow release relay 11 to ground. This energizes relay 11 which in turn energizes relays 12 and 13. As these relays are of the slow release type, all three will remain energized as long as the sending relay l continues to send signals to the line. The operating winding of relay 12 extends through the contacts of the receiving relay 2 to the battery i l for reasons to be explained later. When relay 13 operates, it connects the receiving leg battery 1 through the winding of control relay 7 in the following manner: From battery 14, conductor 15, armature and contact of relay 13, conductor 16, winding of sounder 8 and winding of the control relay 7 to ground. Normally, the control relay circuit would extend from the armature of the receivin relay 2, over conductor 17, break contact of relay 13 and conductor 16 to the winding of control relay 7. In other words, the operation of the relay 13 will disconnect the armature of the receiving relay 2 from the circuit of the control relay 7. Under these conditions any short false impulses or kicks coming in from the line 1 and operating the receiving relay 2 will not release the control relay 7 and hence interfere with signals in loop circuit 6. However, a long break signal such as might be sent from the break key of the distant station would hold the contacts of the receiving relay 2 open for a longer interval sm'iici lease of the slow release relay 12. iis would cause the release of relay 13. The release of relay 13 would open the circuit over condue-tors 15 and 16 from the battery 14 to control relay 7 thereby releasing the control relay 7. This would open the loop circuit 6 to break back over the circuit to the sending station.

Then the control relay 7 releases, the send ing relay 4 will be locked up as a short circuit from the battery 18 is removed from its auxiliary or upper winding and this will operate the relay 9 and release relay 11. V

lVhen the break key at the distant station is released, the receiving relay 2 will close out to cause the reits upper contact and operate the control relay 7 to close the loop circuit 6. The sending relay 4 and the relay 9 will remain operated, however, as the original sending station has now stopped sending and the relay 11 will remain released, preventing the other slow release relays from operating. The breaking station can now send signals over the circuit, the signals being repeated through polar receiving relay 2 and control relay 7 in the usual manner.

If signals are being sent from the loop of this repeater, the sending relay 4: and relay 9 will operate and hold the slow release relays 11, 12 and '13 energized as previously described. It the sending station now stops sending, the sending relay l and relay 9 will come to rest energized and will release relays 11, 12 and 13, successively, after a brief interval. It relay 13 is released, signals can be repeated from the line 1 to the loop 6 without a preliminary long break signal sothat when the circuit has been idle any station can start to send in the usual manner without having its signals blocked by the slowbreak arrangements of the invention.

The key 10 is so connected that when thrown it prevents the slow release relays 11, 12 and 13 from operating and as a precaution against possible contact trouble in the relays, it connects the receiving relay con tact to the control relay 7 directly. The key 10 may be used to disconnect the slow break circuit of the invention in case of trouble or in case its duplex set is used on a circuit that operates full duplex or does 'not require this feature for other reasons.

While this invention has been disclosed in certain specific arrangements which are deemed desirable, it is understood that it is capable of embodiment in many other widely varied features without departing from the spirit of the invention as defined by the appended claims.

What is claimed is:

1. In a telegraph system a repeater set comprising a receiving relay, an incoming line controlling said relay, a loop circuit, a control relay for opening said loop circuit, a control circuit for said control relay, said control circuit being normally completed over the contacts of said receiving relay, and slow releasing means controlled by the transmission of signals over said loop circuit for completing said control circuit around said receiving relay contacts;

2. In a telegraph system a repeater set comprising a receiving relay, an incoming line controlling said relay, a loop circuit, a control relay for opening said loop circuit, a co ntrol circuit for said control relay, said control circuit being normally'completed over the contacts of said receiving relay, slow releasing means controlled by the transmission of signals over said loop circuit for complete ing said control circuit around said receiving relay contacts, and means controlled by said receiving relay for controlling said slow releasing means whereby said control circuit may be restored to its normal state.

3. A transmission line, a telegraph repeater included in said line, means in said repeater responsive to a break signal transmitted in one direction over said line, and means controlled by the transmission of signals over said line in the opposite direction for rendering said break responsive means unresponsive to signals of short duration.

&. A transmission line, a telegraph repeater included in said line, responsive means in said repeater for controlling a break, said responsive means being normally responsive through said repeater in the direction opposed to said break signal for causing said first mentioned responsive means to become selective as to incoming impulse duration.

5. A transmission line, a telegraph repeater included therein, and means in said repeater controlled by signals transmitted therethrough in one direction for preventing signals of short duration coming in from the other direction from interfering with said first mentioned signals.

6. A transmission line, a telegraph repeater included in said line, break-in means associated with said repeater and adjusted to operate on currents of longer duration than. the normal signal currents transmitted over the line, and switching means controlled by the transmitter in said repeater for connecting said break-in means with said line.

7. A transmission line, a telegraph repeater included in said line, and responsive means associated with said repeater for controlling a break signal, said responsive means being operated solely by currents of longer duration than the normal signaling currents transmitted over said line.

8. A transmission line, a telegraph repeator included in said line, and means associated with said repeater for controlling a break signal, said means being responsive solely to incoming currents of longer duration than the outgoing signal currents transmitted over the line.

In testimony whereof, I- have signed my name to this specification this 1st day of December, 1927.

GILBERT S. VERNAM. 

